Application note(PDF) from Silicon Labs on Magnetic stripe reader (MSR) implementation.
Magnetic stripe readers (MSRs) are widely used in many different applications such as point-of-sale terminals and key card readers. The C8051F330 is capable of integrating MSR functionality in a very small space with few external components. The high-speed, high-resolution ADC, coupled with a fast controller core makes this integration possible. This design demonstrates a two-channel MSR function using the on-chip ADC to read information directly from the magnetic read head. Output can be viewed using a PC’s terminal program via an RS-232 connection.